In order to evaluate the diagnostic reliability of stress myocardial scintigraphy, myocardial images were obtained at rest and during stress in groups of patients 1) with coronary disease, 2) with asymmetric septal hypertrophy, and 3) in normal subjects. Myocardial defects in patients with coronary disease appeared relatively specific when compared with normal subjects. However, a significant number of patients with asymmetric septal hypertrophy showed similar defects. In addition, the technique appeared relatively insensitive in that 30 percent of patients with coronary disease had negative studies.